Eur. Phys. J. B 61, 293-297 (2008)
https://doi.org/10.1140/epjb/e2008-00068-2

An experimental study of impulsively started turbulent axisymmetric jets

Department of Chemical Engineering, Indian Institute of Technology-Bombay, Mumbai, 400076, India

Corresponding author: ^a mahesh@che.iitb.ac.in

Received: 28 August 2007
Published online: 20 February 2008

Abstract

An impulsively started turbulent jet injected into quiescent surroundings with a constant inlet velocity has been studied experimentally. Results show that the jet length increases linearly with the square-root of time, over a wide range of Reynolds number calculated with respect to the jet diameter. The celerity factor, x_f/t U, has been found to be nearly constant at 2.47 throughout with a 5% variance. Here, x_f is the jet length, t is the time and U is the jet exit velocity. These results compare favourably with earlier results reported at lower Reynolds numbers. Finally, we present a simple model based on the integral energy balance of the turbulent boundary layer equation for an impulsively started turbulent axisymmetric jet. The model predicts a jet length that scales as, where d is the nozzle diameter and B(≈6.0) is the velocity-decay constant. This gives a celerity factor, in close agreement with the experiments.